Epidemiology

The population prevalence of antiphospholipid syndrome is unknown but it is estimated that the condition may affect around 0.5% of the population (1).

• it is mainly seen in young women of fertile age and rarely occurs in children
• according to a large international cohort
  • the mean age at diagnosis was 34 years
  • male:female ratio was 1:3.5 for primary disease and 1:7 for secondary diagnosis associated with SLE (1)
  • clinical manifestations of APS generally affect young and middle-aged adults, with 85 % of patients being between 15 and 50 years of age (2)
• about 50% of patients with antiphospholipid syndrome have the primary form of the disease.
• about 1/3 of patients with SLE have antiphospholipid antibodies but not all of those have the syndrome.
• in about 2% of the normal population, detectable antiphospholipid antibodies are present. In 0.2% the titre is high.
• the clinical course and severity of the lupus is worsened by the presence of the antiphospholipid syndrome.
• the annual risk of thrombosis in untreated patients is 1 in 3 per year.
• less than 1% of patients develop the catastrophic form with half of them appearing denovo without previous thrombotic events (1)

Notes:

• based on an analysis of 120 full-text papers, the AntiPhospholipid Syndrome Alliance for Clinical Trials and InternatiOnal Networking (APS ACTION) calculated mean frequencies for positive APL tests for different clinical presentations, as follows (3,4,5):
  • 17 % for patients with stroke under age 50 years,
  • 14 % for patients with stroke,
  • 11 % for patients with myocardial infarction,
  • 10 % for patients with deep vein thrombosis, and
  • 9 % for patients with recurrent pregnancy loss
• however, several study limitations make it difficult to make precise estimates of APL frequencies: the majority of the papers were published before 2000, tests for all three APL criteria were performed in only 11 % of papers, APL confi rmation six to twelve weeks apart was performed only in approximately 20 % of papers, and nearly half of the papers were retrospective studies (2,5)
• prevalence in other autoimmune connective tissue diseases (e. g., systemic sclerosis, Sjogren's syndrome, dermatomyositis, and rheumatoid arthritis) ranges from 6 to 15 % (5)
• prevalence of APL is estimated to be approximately 1-5 % in the general population, with an increasing prevalence with older age. Concomitant APL positivity is frequently observed with infections, drugs, and malignancies; however, in the majority of these cases, APL titres are transient and low, and it is questionable whether these APL titres increase the risk of vascular events or adverse pregnancy outcomes (2)

Reference:

• Cohen D et al. Diagnosis and management of the antiphospholipid syndrome. BMJ. 2010;340:c2541
• Sciascia S, Sanna G, Khamashta MA, Cuadrado MJ, Erkan D, Andreoli L, et al.; on behalf of APS Action. The estimated frequency of antiphospholipid antibodies in young adults with cerebrovascular events: a systematic review Ann Rheum Dis. 2015;74:2028-33
• Ruffatti A, Del RT, Ciprian M et al. Risk factors for a first thrombotic event in antiphospholipid antibody carriers: a prospective multicentre follow-up study. Ann Rheum Dis. 2011;70:1083-6.
• Medina G et al. Prevalence of metabolic syndrome in primary antiphospholipid syndrome patients. Autoimmun Rev. 2011; 10:214-7.
• Andreoli L, Chighizola CB, Banzato A, Pons-Estel GJ, Ramire de Jesus G, Erkan D. The estimated frequency of antiphospholipid antibodies in patients with pregnancy morbidity, stroke, myocardial infarction, and deep vein thrombosis. Arthritis Care Res. 2013;65:1869-73.